1) Labour MPs realise Martin's early resignation gives them an unexpected chance to impose on Cameron someone whom the Tories won't like - they still have a majority, after all. After the election, they won't.
4) Field, being an honest chap, doesn't go ahead because he isn't backed by Labour MPs and thinks the Speaker should have the trust of the whole House.
5) Bercow has no such scruples, and is delighted to be used by Labour to irritate Cameron. But the idea of a Tory still doesn't appeal to Brown, the most factional of all politicians.
7) Beckett, for all her defects, is seen by the Tories as the best 'stop Bercow' candidate. She is, after all, being promoted by Brown's henchmen. Sure, they'd like George Young ideally, but even Beckett is better than the idea of Bercow's smarmy face smiling down at them from the Speaker's chair.
9) The Speaker election is then driven by factionalism, revenge, an 'up-yours' attitude not just to politcial enemies but the public as a whole.
Beckett is described as the "anti-reform" candidate - but that implies there is a pro-reform candidate. John Bercow is not that man. He's not outraged by the abuse of expenses: he was going nowhere in the Tory party, thought about defecting to Labour (and Labour sources tell me they were confident he would have crossed the floor had David Davis become leader) and is offering himself to Labour MPs as an irritation to Cameron. Rather than be someone the House respects (like Betty Boothroyd), the Speaker will be the product of one of these games of spite and revenge that Westminster politicians love to play with each other. George Young and Alan Haselhurst would, in my view, chair debates better than the other candidates - but neither can give the Commons the reform it so badly needs.
I leave you with the verdict of Stephen Pound:
But when you ask poachers to choose a new gamekeeper, what do you expect?“
“I think it is potentially a fatal mistake. It is a depressing example of MPs looking inwards to their own advantage when we really should be looking outwards. This is great opportunity for us to present a new, fresh face for Parliament and a lot of it looks like the same old, stale corruption, I fear"